1. Field of the Invention
The present invention relates to a method of conducting a continuous multi-phase catalytic reaction and is particularly, though not exclusively, applicable to the catalytic conversion of syngas, produced by the reforming of methane, to hydrocarbon fuels, by a Fischer-Tropsh type of synthesis. Other reaction systems to which the method is applicable include various slurry reactions for the production of petrochemicals, the production of oxygenates from synthesis gas and dehydrogenation reactions.
2. Description of the Invention Background
Three-phase catalytic reaction systems are used in a number of chemical processes and their application in the petrochemical industry appears to be increasing. Of the three-phase systems in use, mechanically agitated, loop and bubble column slurry reactors contain small catalyst particles dispersed in the liquid. In most applications, the liquid will have to be separated from the slurry to remove liquid products or for catalyst regeneration purposes. In those cases where the liquid is an inert medium, occasionally, it may have to be replaced due to degradation or the build-up of impurities.
Mechanically agitated slurry reactors are particularly convenient for batch process due to the low mass-transfer and heat resistance. These features also make them suitable for the determination of reaction kinetics in the laboratory. A serious disadvantage and limitation of this reactor type, however, is the difficulty in the separation of catalyst particles in any continuous operation.
Commercially, it is only mechanically agitated reactors that are used in the hydrogenation of double bonds in oils from cottonseed, soybean, corn, sunflower etc. By employing a nickel catalyst, the products include margarine, shortening, soap and greases. The choice of reactor is based on the low diffusivities and high viscosities of the fatty oils. Fixed-bed operation has been proposed due to the advantage of completely catalyst-free products without filtration. A number of other hydrogenation reactions are also carried out in agitated reactors, e.g. the hydrogenation of nitrocompounds.
The operation of bubble column slurry reactors is simple, since mechanically moving parts are avoided. Combined with the low diffusional resistance and efficient heat transfer, these reactors are attractive for many industrial processes. However, solid-liquid separation is usually performed outside the reactor in elaborate filtering and settling systems. The catalyst slurry is to be recycled to the reactor, sometimes with the use of a slurry pump. Thus, serious problems may be encountered in the continuous operation of bubble column slurry reactors.
As world oil resources diminish it is becoming more attractive to use natural gas as an energy source and methods of upgrading this to higher hydrocarbon fuels are increasing in importance.
It is therefore an object of the invention to provide a continuous method of conducting a multi-phase catalytic reaction which does not suffer the drawbacks of the prior art.
It is a particular object of the invention to provide such a process which is well suited to use in the conversion of natural gas via syngas to diesel fuel.